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SWITGHBOARD FOR TELEPHONE GENTRAL OFFICES. No. 280,662 I I Patente d July 3, 1883.

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-THOMAS J. PERRIN, OF BROOKLYN, NEWV YORK.

SWITCH-BOARD FORTELEPHO'NE CENTRAL OFFICES.

SPECIFICATION forming part of Letters Patent No. 280,662, dated July 3, 1883.

Application filed January 1-2, 1883.

(No model.)

new and useful Improvements in Switch Systems and Boards for Telephone and Telegraph Exchanges, of which the following is a specification.

This invention relates to switch-boards for making connections between the various subscribers lines terminating at the central office of a telephone-exchange, its objects being to so divide and arrange the whole number of line terminals into connected sections as to promote rapidity and convenienceof making connections, to enable the operators of the various sections to ascertain quickly whether or not any line is in use, and to generally simplify the apparatus and operations of a cen tral office. I

To these ends the invention consists in cer tain novel combinations and arrangements of line terminals and central-office circuit-connections, which will be hereinafter particularly described and explained with reference to the accompanying drawings, in which Figure 1 is a diagram representing the sectional switch-boards of a central office, and Fig.2 is a fragmentary cross-section between a row of terminal plates.

For illustration, it will be understood that nine subscribers lines enter the central office, and these lines are provided with terminal plates, the whole number of which is divided in three sections arranged on different boards, (designated in the drawings as section-board No. 1, section-board No. 2, and sectionboard N0. 3.) The terminal plates proper are indicated by simple numerals, and the manner in which they are set in the board is shown in Fig. 2. They are made of metal, and are separated byintervening spaces, preferably of different widths, into the wider spaces of which suitable plugs may be inserted for connecting any two plates electrically. Each line is provided with a plurality of terminal plates, arranged as shown and described in an application for patent heretofore filed by me on the 22d day of December, 1882, Serial No. 79,978, and I need therefore simply state that each line has its plates so arranged that one or an other of them may be connected by plug with a plate of any other line having terminals on the same board, the plates on each board, as shown in the drawings, being arranged in rows in numerical order, except that the number which begins a row is repeated generally after every two following numbers; but they may be T T T at the respective boards, and through them to ground, and said board has, in addition to its line terminals, connecting plates marked with numerals and the letter a. The boards following No. 1 have ground-connecting plates numbered, and also lettered b, and all the boards have communicating-plates numbered, and lettered c.

The terminal blocks 3 4 5 6 7 S 9 in boards 1 2 3 all serve the same purpose, being special terminal blocks connecting through listeningstrip, and so arranged that they are separate and distinct, electrically insulated from each other, and not a continuous strip, so that removing the connecting-plug from between each or either of said blocks and the block or terminal adjoining and placing it elsewhere serves to break the connection between each or either of said blocks and the listening-plate, so that no call at any other board or portion thereof can-be made, the circuit havin been broken.

Similarly-numbered line-connecting plates are connected together, as shown in the case of plates marked 3, 5, and 9, by broken lines, which represent the connecting-wires, these wires running in any convenient manner or direction 011 the back of the-board, and each series of similarly-numbered plates is connect ed with corresponding calling terminal plates as, for instance, the plates 1 are connected with plates 1, 2 with 2, 3 with 3, and so on.

Each line has a calling terminal plate on section-board No. 1, and said plates are normally plugged to ground through the strip L and all the telephones, so that any communication to the central office over any line will be heard by all the listening operators, each operator attending only to the calls of subscribers on his board.

In dividing the whole number of terminal plates in sections the rule is observed to allow to each operator a given number of lines, and have all the lines represented by plates on section-board No. 1, though the operator of said board will attend to only such lines as are allotted to him. Then plates of all the lines specially assigned to operator No. 1 are omitted from section-board N o. 2, though all the remaining lines are represented thereon, while plates of these lines specially allotted to the attention of operators N o. 1 and N o. 2, respectively, are omitted from. section-board No. 3, upon which all the restof the lines are represented, and so on, if there should be more seetion-boards.

Although each o'perator hears the calls made over all the lines, they take notice only of those over their own lines. In the present instance lines Nos. 1 and 2 are assigned to operator at section-board No. 1, lines 8 and 4 to operator No. 2, and lines 5, 6, '7, 8, and 9 to operator No. 3.

I will now explain the course of a subscriber s line-circuit after it enters the central office, and for this purpose will take the line 9, as that being the highest number, it will necessarily have plates on all the boards. Its connections can be traced by the dottedlines, from which it will be seen that line No. 9 first connects with its properly-numbered terminal plate in the top row of section-board No. 1, from which plate connection is made to the similarly-numbered plate in the next row, thence by normal plug-connection to a communicating-plate, 9, and from this plate to section-board No. 2and its platesnumbered 9 to the communicatingplate 9 of said board, thence by normal plugconnection to plate 9", and thence to sectionboard No. 3, its plate 9, and communicatingplate 9, thence by normal plug-connection to the adjacent ground-connecting plate 9", thence to calling terminal plate 9 0f section-board No. 1, and by normal plug-connection to the listening-circuit and ground-connecting plate L, whence it goes through the telephone to ground. All the other line-connections of the office will be similar, each finally reaching the strip L. Lines Nos. 1 and 2 of course have no connection with section-boards Nos. 2and 3, and lines 3 and 4 have no connection with board No. 3, no line having intermediate connection with any board upon which it is not represented by line-connecting plates.

The general rule of operation is that an opetator takes notice of only such calls as come over his special lines, or over lines having higher numbers calling for connection with his special lines.

I will now explain the method of proceeding by the operators: We will suppose that a call comes over line N o. 1 for connection with line No. 9. The call is heard by all the operators but only operator N0. 1 responds to it. He

makes no preliminary tests or inquiries as to whether or not line No. 9 is in use, but simply takes the plug from between his calling terminal plate 9? and the listening-circuit and ground-strip L and inserts it 011 the opposite side of said plate 9that is, between it and the calling circuit-strip C. This disconnects line No. 9 from ground through listening-circuit and connects it in the office callingeir cuit, and the operator then, by any suitable calling apparatus, preferably that shown and described in my previous application before referred to, sends a call over line No. 9. If he receives an answer, he removes the plug from between the calling-strip and plate 9 and in serts it between adjacent plates 1 and 9 in the top row of his line-connecting plates. The desired connection is thus completed. If he receives no answerto his call on line 9, he knows that the line is in use, or connected with some other line not included in his special allotment. He could learn by a mere glance at his plates if it were connected to one of his own lines. If the original call should come from No. 9 for connection with No. 1, the operation is the same as above explained.

If a call should come from line No. 3 for connection with a higher-numbered line-say No. 9only operator No. 2 should respond to it, and his proceeding would only differ from that of operator No. 1 in that as there is no common listening-circuit and ground-strip on his board he would take the plug from between his plate 9 and his ground-connecting plate 9", thus disconnecting line 9 from ground, and insert it between plate 9 and calling-strip C, and call line 9. If he gets an answer, he

transfers the plug to his top row of plates, be-

tween plate 3 and plate 9, and completes the desired connection. If he gets no answer, he simply returns the plug to its normal position, thus leaving line 9 in its normal connection to his board. Calls over any of the lines having plates on board N o. 3 would be treated by operator N o. 3 in a similar manner.

It will be observed that an operator on receiving a call makes no preliminary tests or inquiries whatever, but proceeds precisely as he would if he knew the called line to be not in use, and only pauses in the regular necessary steps when he can go no further because of the failure of the called line to respond, so that no delay whatever is experienced if the called line is ready for connection with the one calling.

In diyiding the whole number of terminal plates into sections the aim will be to give the operators, as nearly as possible, equal amounts ofwork. It will be obvious that ifthe lines were simply equally divided among the boards that is, each given the same number of special lines to and from which to make connections-- the operator at section-board No. 1 would have much the largest amount of work to do, as all the lines are represented on his board, and he must make connections from his special lines to all higher numbers on his board. In practice, therefore, each succeeding sectional board omitted from the subsequent sections, substanin the series should have assigned to it a greater number of special lines than the board preceding it, and thus while a given board will havealarger number of higher numbers called by lower numbers it will not have so many lower called by higher numbers as does the succeeding board.

Having thus described my invention, what I claim is 1. A switchboard for a centraltelephone or telegraph officeor exchange, consisting of a series of sections, one of which is provided with terminal plates for all the linesentering the central office, the number of terminal plates in the remaining sections being diminished successively by omitting from each the termi nal plates for such lines as have been assigned to the preceding sections for special attention, substantially as described.

2. A switch-board for a central telephone or telegraph office or exchange, consisting of a series of sections, each of which is provided with a permanent call-connection strip, and the first has terminal plates representing all the lines entering the office or exchange, each subsequent section having a series of terminals less than its predecessors, those specially assigned for attention to any section being tially as described.

3. A switch-board for a central telephone or telegraph station or exchange, consisting of a series of sections, each provided with terminals for such of the lines entering the office or exchange as are assigned to it for attention, and terminals for such lines as are connected to the subsequent sections, substantially as described.

4, A series of switch-boards, each having line-connecting terminals arranged for plugconnection with each other, substantially as described, calling-terminals permanently con nected with said lines, a calling-circuit terminal strip arranged for plug-connection with said permanently-connected calling-terminals, and ground-connection with said calling-terminals, the calling-circuit terminal strips be ing connected from board to board, and the ground-connecting terminals of each-succeeding board connected with the calling-terminals of a preceding board, substantially as set forth.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

THOMAS J. PERRIN.

- WVitnesses:

CHARLES A. RANDALL, JOHN WIENHOLD. 

